radioactivity (paper 1)

radio active decay

- the process where an unstable atomic nucleus spontaneously transforms into a more stable one by releasing energy in the form of radiation, such as alpha, beta, or gamma particles

it is completely unaffected by physical conditions like temp

radioactive substances emitt ionising radiation. Ionising radiation knocks electrons off atoms, creating positive ions.

Types of ionising radiation: alpha, beta, gamma

they release neutrons as they decay to balance their atomic and mass numbers

radioactivity

the emission of ionizing radiation or particles caused by the spontaneous disintegration of atomic nuclei.

radioactve particle facts

some atoms are naturally radioactive/emit radiation

-radiation is emitted randomly from unstable nuclei and it decays to become more stable

-when a nuclei decays, it is changed

-The mass/energy/compostitio of the nucleus is changed and a radioactive particle is emitted.

what are alpha particles composed of

2 protons and 2 neutrons He

4

…..A

2

use this in a nuclear equation

alpha mass

4

alpha charge

2

alpha penetrating power

skin or paper (weak)

alpha range in air

5-6cm

alpha ionizing ability

strongly ionizing

alpha use

becayse of their penetrating range and ionizing ability are ideal for detecting smoke

alpha decay

2 protons and 2 neutrons = an alpha particle

unstable nucleus → alpha decay → an alpha particle is lost from the nucleus

alpha particles are relatively big and heavy and slow moving. This means they dont penetrate very far into materials and are stopped quickly.

because of their size they are strongly ionizing - they bash into alot of atoms and knock electrons off them before they slow down which creates alot of ions.

what are beta particles composed of

1 high energy electron 0

-1 e

beta mass

0

beta charge

-1

beta penetrating power

moderate

aluminum (a few mm thick)

beta range in air

1m (moderate)

beta ionizing ability

moderately ionizing

beta use

used for thickness monitoring bc it has enough penetrating power for thin materials

beta decay

fast moving electron released by a nucleus

when a nucleus decays by beta decay, a neutron turns into a proton in the nucleus

this increases the the charge of the atom by 1 so the nucleus ejects one electron (an electron) so the mass number is unchanged

unstable nucleus → beta decay → a neutron turns into a proton and a beta particle is released

beta particles are quite fast and small

0

…..B

-1

use this in a nuclear equation

What is gamma composed of

gamma is a wave

e.g. 0

0 g

gamma mass

0

gamma charge

0

why does gamma have no mass or charge

because it is a form of high energy radiation, not a particle

gamma penetrating power

lead or concrete

gamma range in air

unlimited

gamma ionizing ability

weakly ionizing

gamma use

tracers because of their high penetrating power allows them to pass through the body to be detected outside. They are also weakly ionizing so wont mutate any cells whilst inside the body

gamma decay

waves released by the nucleus

they are weakly ionising because they tend to pass through the air rather than collide with atoms but eventually they hit something and do damage

why dosent the emmision of gamma rays change the atomic number (mass or charge) of a nucleus like alpha and beta.

because they have no mass or charge themselves

alpha behaviour in a magnetic field

affected but not much

beta behaviour in a magnetic field

the biggest reaction because its charge is bigger compared to its mass

gamma behaviour in a magnetic field

passes straight through bc no charge

what do you use to measure radiation

Geiger-Muller tube

units for radioactivity

bequerels - Bq

1Bq = 1 decay per second

(count rate also means decays per second)

units for radiation dose

sieverts - Sv

1000 mSv = 1 Sv

half life

the time taken for half the radioactive nuclei in a sample to decay

different isotopes' activities drop offs vary

why do older sources emitt less radiation

each time a radioactive nucelus decays to become a stable nucleus, the activity will decrease.

why do we calculate half life

because it will never reach 0 so we use half life to get an idea how quickly the activity will drop off

what does a short half life mean

the activity falls quickly because the nuclei are very unstable and decay rapidly

dangerous because they emit alot of radiation at first but become safe quickly

what does a long half life mean

activity falls slowly because most nuclei dont decay for a long time

they just sit there releasing small amounts of radiation over a long period of time

this can be dangerous if exposed for a very long time.

practice calculating half life

What is the curve called to show half-lives of a sample on a graph

exponential curve

radioactive contamination

the unwanted presence of materials containing radioactive particles

radioactive irradiation

The process of exposing an object to nuclear radiation

- dosent make a object radioactive

- used for sterilization because rays pass through killing bacteria and no trace left behind

 how to manage the use of radioactive  sources during irradiation to protect against hazards.

• Time: Minimize exposure duration by planning work, performing "dummy runs," and operating efficiently.

• Distance: Maximize distance from the source. The intensity of radiation decreases according to the inverse square law—doubling the distance reduces exposure to

  . Use long-handled tools (tongs) for handling sources.

• Shielding: Use appropriate barriers, such as lead-lined containers, lead bricks, or concrete walls, to stop or reduce radiation intensity, especially for gamma and X-ray sources

compare the hazards associated with contamination and irradiation.

• Location of Source: Irradiation comes from an external source. Contamination involves the radioactive source physically on or inside an object or body.

• Duration:

  Irradiation stops when the source is removed. Contamination lasts as long as the material remains.

• Most Dangerous Radiation Type:

  • Irradiation: Beta and gamma are dangerous due to high penetration.

  • Contamination: Alpha particles are highly hazardous if ingested/inhaled because their high ionization causes severe localized damage.

• Protection: Irradiation is managed via shielding, distance, and time. Contamination requires decontamination, protective clothing, and specialized handling.

• Systemic Effects: Contamination causes internal organ exposure, while irradiation primarily causes external damage

contamination and irradiation can cause different amounts of harm based on radiation type:

• outside the body, gamma and beta are most dangerous because highly penetrating

• inside the body, alpha is most dangerous because they cannot get out and do all their damage in a very localised area.

effect of radiation on living cells

lower doses tend to cause minor damage to cells without killing them, This can give rise to mutant cells which divide uncontrollably. The cells keep dividing making more cells can form a tumor. This uncontrolled cell division is cancer.

Higher doses tend to kill completely, which causes radiation sickness if alot of body cells are killed at once.

the extent of harm depends on two things:

• how much exposure you have to radiation

• the energy and penetration of the radiation.

how radiation can harm

- cataracts in the eye

- cancer

- infertility

- radiation burns on the skin

- damaged immune system

- vomiting

- internal bleeding

safely handling radioactive materials

- limit exposure time

- don't handle, use tongs

- wear protective clothing

why do radioactive isotopes have a very wide range of  half-life values.

because the stability of an atomic nucleus depends on its specific nuclear structure, particularly the ratio of protons to neutrons

explain why the hazards associated with radioactive material differ according to the half-life involved.

Radioactive material hazards differ by half-life because it determines the rate of decay and radiation emission. Short half-lives (e.g., Iodine-131) release high, intense doses quickly, posing acute, immediate dangers. Long half-lives (e.g., Plutonium) decay slowly, causing lower-dose, long-term contamination risk

radiation dose

measure of the risk of harm to your body due to exposure to radiation

measured in sieverts (Sv) and millisieverts (mSv)

why should the findings of studies into the effects  of radiation on humans should be published and  shared with other scientists.

Publishing studies on human radiation effects ensures safety standards by enabling independent verification, peer review, and reproducibility of findings. Sharing this data allows scientists to validate risk assessments, improve medical practices, and establish accurate safety limits for public exposure, ultimately reducing health hazards

background radiation - natural

50% radon gas from the ground

13% the ground

13% medical

13% cosmic rays

13% food and drink

background radiation - artificial

mostly medical

5% nuclear weapons

<2% other

 factors that affect the level of  background radiation and radiation dose. 

• Geological Structure: Rocks and soil differ in naturally occurring radioactive nuclei (uranium, thorium, potassium-40). Areas with granite have higher radiation than those with sedimentary rock.

• Altitude and Location: As altitude increases, atmosphere shielding decreases, leading to higher cosmic radiation doses.

• Radon Gas: The biggest contributor, radon gas is released from soil/bedrock, accumulating in enclosed spaces like basements.

• Weather: Atmospheric conditions can cause radioactive materials from nuclear tests or natural sources to settle.

• Man-made Sources: Fallout from nuclear weapons testing, radioactive waste from accidents (e.g., Chernobyl, Fukushima), and medical radiation (X-rays, CT scans) affect the total, especially in affected areas

radiotherapy

- irradiates the body to kill cancer cells

tracers

- gamma rays

- pass through the body

- least ionizing

- half-life, a few hours

the amount of radiation you are exposed to can be affected by your location. Some examples:

• underground rocks

• high altitudes (cosmic rays)

the amount of radiation you are exposed to can be affected by your occupation. Some examples:

• nuclear industry workers and uranium miners

• radiographers

• any miners

nuclear fission

the process of splitting large unstable nuclei

where is controlled nuclear fission taken place

nuclear reactor

common substances used for nuclear fission

uranium-235 and plutonium-239 because they are large unstable nuclei

uk nuclear fission source

uranium-235 because it is naturaly occuring whereas in america plutonium-239 is naturally occuring

How to induce nuclear fission

fire a neutron at uranium-235. the nuclei will become unstable as uranium-236 and splits into 2 daughter nuclei releasing 3 neutrons and gamma radiation

daughter nuclei

they will be roughly the same size

energy produces from nuclear fission

mostly released as kinetic energy (due to fast moving neutrons and daughter nuclei) and energy in form of gamma radiation

chain reaction

-keeps going once started

-produces more and more energy

controlled nuclear fission

nuclear power station

uncontrolled nuclear fission

nuclear bomb

nuclear reactor/core

First a neutron strikes a uranium atom causing it to split, giving off 2 daughter nuclei, 3 neutrons and gamma radiation. the 2 daughter nuckei get another nuclei fired at them for more fission, the neutrons get absorbed by the control rods and the gamma radaiation is an exothermc reaction so the fuel rods heat up causing the water to turn into steam.

making electricity in a nuclear power station

-nuclear rods get hot by fission

-water turns to steam

-turbine turned by steam

-turbine turns generator

advantages of nuclear fission

no co2 produced

no noise

no burning

disadvantages of nuclear fission

non-renewable energy source

uranium and plutonium are expensive and hard to access

radioactive waste is produced!

disposing nuclear waste

nuclear waste is radioactive

has a long half-life so remains dangerous

stored underwater or underground for at least a year before being dealt with

stored in lead lined containers

nuclear fusion

The joining of two light nuclei to form a larger, bigger, heavier nucleus

e.g. 1 2 3

1 H + 1 H = 2 H

the famous equation that describes the amount of energy released from the nucleus in a nuclear reaction

e=mc²

where does nuclear fusion occur naturally

sun/stars

energy from fusion

-fusion releases energy in the form of gamma radiation

-some form of energy that is released is due to the kinetic energy of the particles

-most of the energy from nuclear fusion is released as radiation

-when fusion occurs, some of the mass (particles) is converted into energy

e.g. e=mc^2 c=speed of light m=some of the mass to energy=e

fusion on earth - positives

-releases lots of energy

-hydrogen is plentiful and cheap

-hydrogen and helium are fairly safe

-almost no radioactive waste

-no riskof nuclear accident

-no co2 produced

fusion on earth - disadvantages

because the 2 light nuclei have the same charge, a force of replusion keeps the 2 hydrogen nuclei (protons) apart. In order for fusion to happen, very high temperatures are needed to force the two nuclei together. This means it is using more energy than it produces

a fusion reactor - 'tokamak'

At the moment, making fusion happen on earth si expensive and difficut, and uses more energy than it produces.